package ex2;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Locale;

public class Main {

	public static void main(String[] args) throws IOException {
		
		InputStreamReader ir = new InputStreamReader(System.in);
		BufferedReader in = new BufferedReader(ir);
		
		Double pi = 3.14159, raio, area;
		raio = Double.parseDouble(in.readLine());
		area = Math.pow(raio, 2) * pi;
		
		System.out.format(Locale.ENGLISH, "A=%.4f\n", area);

	}

}